David B. Pilcher

Anti-CD 18 monoclonal antibody slows experimental aortic aneurysm expansion☆☆☆★★★

PURPOSE Inflammation has been implicated as a contributing factor in the expansion of abdominal aortic aneurysms (AAA). To test this hypothesis, we examined the effects of a monoclonal antibody (MAB) to the leukocyte CD18 adhesion molecule on the expansion of experimental AAA. METHODS Aneurysms were induced by perfusion of an isolated segment of the infrarenal aorta with elastase in 22 normotensive (WKY) and 17 genetically hypertensive (WKHT) rats. Animals of both strains were randomly allocated to control or MAB-treated groups (MAB, 5 microgram/100 gm body weight intraperitoneally, daily, beginning on the operative day for a total of four doses). The activity of the MAB against rat leukocytes had first been determined by in vitro immunofluorescence flow cytometry. Aortic size was directly measured initially and on day 14. At that time, a segment of aorta was stained with hematoxylin and eosin and mononuclear leukocytes and neutrophils were counted in each of 10 microscopic fields (400X). RESULTS The initial aortic size in all animals was 1.11+/-0.15 mm. All groups developed aneurysms significantly larger than the initial aortic size (p<0.01). However, the MAB-treated animals had significantly smaller aneurysms than the untreated controls (mm): WKY: 3.63+/-1.26, WKY-MAB: 2.08+/-0.30, WKHT: 4.54+/-1.86, WKHT-MAB: 2.37+/-0.40, p<0.0001. There also were significantly fewer monocytes in the MAB-treated normotensive rats: WKY:35.5+/-29.9, WKHT:40.6+/-28.8, WKY-MAB: 8.9+/-8.5, WKHT-MAB: 32.3+/-25.7, p=0.03. Neutrophil counts did not differ significantly between the groups. CONCLUSIONS Treatment with anti-CD18 monoclonal antibody slows the expansion of AAA in this experimental model. The associated inflammatory process at day 14, as indicated by monocyte infiltration, is reduced, but this effect may be opposed by the presence of hypertension. Further evaluation of the role of leukocytes and adhesion molecules in the expansion of AAA is warranted.

Effects of hypertension and propranolol upon aneurysm expansion in the Anidjar/Dobrin aneurysm model.

Propranolol has been suggested to slow aortic aneurysm (AAA) expansion by a mechanism independent of simple blood pressure (BP) reduction. To investigate this hypothesis, we designed a series of experiments to examine the effects of hypertension and propranolol upon AAA expansion. Using an established animal model, we induced AAA in normotensive and genetically hypertensive rats by perfusion of the isolated infrarenal aorta with elastase for two hours. Systolic tail BP was monitored with a plethysmograph. AAA size was measured directly with a micrometer on postoperative days 7 and 14. All data are expressed as the mean +/- standard deviation (SD). BP (mmHg) was significantly higher in hypertensive rats: 164 +/- 15 versus 119 +/- 7 (p < 0.001). AAA were also significantly larger in hypertensive rats with a mean expansion rate (mm/day) nearly twice that of normotensive animals: 0.13 +/- 0.09 versus 0.07 +/- 0.03. In a second series of animals, propranolol treatment was compared to placebo. In those animals, hypertensive propranolol-treated rats had significantly smaller AAA than placebo-treated controls (p < 0.05). There was no difference in normotensive animals but these rats had an unexplained paradoxical rise in BP with treatment. In this model, hypertension increases the expansion rate of AAA. Propranolol reduced the size of AAA in hypertensive animals, at least in part because of a decrease in BP. Other possible mechanisms of propranolols action may be operative and require further study.

A prospective randomized trial of the Lazarus-Nelson vs. the standard peritoneal dialysis catheter for peritoneal lavage in blunt abdominal trauma.

One hundred consecutive injured patients with blunt abdominal trauma requiring peritoneal lavage were prospectively randomized to placement of lavage catheters with an open or percutaneous technique. The Lazarus-Nelson catheter, placed by Seldinger wire technique, was compared to a standard dialysis catheter, placed by direct visualization and incision of the peritoneum. Placement of the catheter was consistently faster using the percutaneous method; no difference was noted in time of lavage, volume recovered, or complications. When not contraindicated, the percutaneous technique was widely preferred by study participants.

Morphology Predicts Rapid Growth of Small Abdominal Aortic Aneurysms

This study evaluated CT scans of small abdominal aortic aneurysms (AAAs) (< 5 cm) to assess anatomic features associated with rapid expansion. Serial CT scans obtained at least 10 months apart (mean 15 months) from patients with small AAAs were reviewed. Each cross-sectional image of the AAAs was analyzed using a computer-assisted design program. The circumference of the AAA in each CT image was divided into eight equal arcs, from which the apparent radius of curvature (Rc) for each segment was calculated. Flattening of the wall curvature results in an increased segmental Rc. The CT scans of nine patients with expanding AAAs (expansion ≥0.5 cm/yr) were compared to those of 10 patients with stable AAAs (expansion <0.2 cm/yr). To adjust for differences in AAA size, the Rc for each segment was normalized by dividing each individual Rc by the average of the eight Res (RcAvg) calculated for that cross-sectional CT image. Analysis of variance showed that the left posterolateral segments in expanding AAAs had larger Rc/RcAvg ratios than those segments in stable AAAs (1.14 ± 0.19 vs. 0.80 ± 0.09, p < 0.02). Laplaces law indicates that the left posterolateral segment in AAAs that grow more rapidly is subjected to greater wall tension. Flattening in the curvature of the left posterolateral wall segment was significantly associated with an increased rate of expansion in small AAAs. This finding, readily derived from standard CT scan images, may predict which small AAAs are more prone to rapid expansion.

Patterns of splenic injuries seen in skiers

Splenic rupture secondary to skiing appears to fall into two distinct epidemiological patterns: high-speed impact with stationary objects and simple falls (mogul injury). Of 18 splenic injuries seen at a referral hospital over 12 years, six were high-speed collisions with trees, lift towers or other solid objects. Twelve were low-speed falls impacting on moguls, the ski trail or low-speed impact with a trailside object (stump or rock). Those who sustained low-speed injuries frequently skied down the mountain afterwards without assistance (8/12), and had no other significant concomitant injuries other than minor renal contusions compared with the collision group (P < 0.005). The rate of splenic salvage was also higher in this group than in the collision group (68 per cent vs 17 per cent). The six high-speed collision splenic injury victims were all transported down the mountain by toboggan, and all had significant associated injuries. The incidence of concomitant renal injuries with splenic injuries in both groups was higher than in other reported series (10 of 18 patients). Some of those who skied down the mountain themselves sought medical attention only when they experienced haematuria. There were no significant differences in the length of stay in hospital, or intensive care units (ICU), or transfusion requirements or complications between groups. It is suggested that those who ski down the mountain themselves and present in a delayed fashion to medical/first aid facilities may still have serious abdominal injury but have a potentially higher rate of spleen salvage.

Renal failure after embolization of a prosthetic mitral valve disc and review of systemic disc embolization

Embolization of discs from various prosthetic mitral valves produces fulminant cardiac failure with possible survival after emergent mitral valve prosthetic replacement. The embolized discs lodge in the aorta at various levels parallel to the blood stream and have not occluded distal flow. Some embolized discs have been left in the aorta for as long as 12 years. An embolized disc left in the abdominal aorta produced renal artery occlusion 5 years after embolization in the reported case. A previous case produced mesenteric ischemia after 1 month. Localization of embolized discs has at times been difficult with success and failure by plain x-ray films, ultrasound, angiography, and CT scans in some cases. Since embolized discs have not produced acute problems with ischemia, delay of retrieval after emergent mitral valve replacement does not seen detrimental. Late complications may occur as with the present case and removal of asymptomatic embolized discs seems advisable and prudent.

Ambulance critique review

Ambulance critique review sessions have been used as a method of conducting peer review for ambulance personnel and emergency department staff, including medical students. Such a review permits recognition of excellence as well as constructive criticism of actual performance. A forum for review of practical techniques and pathophysiology is provided.